Method and system of sensing airflow and delivering therapeutic gas to a patient

ABSTRACT

Sensing airflow and delivering therapeutic gas to a patient. At least some of the example embodiments are methods including: titrating a patient with therapeutic gas during a period of time when a flow state of breathing orifices is in a first state, the titrating results in a prescription titration volume; and then delivering the prescription titration volume of therapeutic gas to the patient when the flow state of the breathing orifices is in a second state different than the first state, the delivering only to the breathing orifices open to flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US2015/054391 filed Oct. 7, 2015 and titled “Method and System ofSensing Airflow and Delivering Therapeutic Gas to a Patient”, whichclaims the benefit of U.S. Provisional Application No. 62/060,617 filedOct. 7, 2014 and titled “Selective Delivery of Therapeutic Gas”. Bothapplications are incorporated by reference herein as if reproduced infull below.

BACKGROUND

Patients with respiratory ailments may be required to breathetherapeutic gas, such as oxygen. The therapeutic gas may be delivered tothe patient from a therapeutic gas source by way of a nasal cannula.

Delivery of therapeutic gas to a patient may be continuous, or in aconserve mode. In continuous delivery, the therapeutic gas may besupplied at a constant flow rate throughout the patient's breathingcycle. A significant portion of the therapeutic gas provided incontinuous delivery is wasted (i.e., the therapeutic gas deliveredduring exhalation of the patient is lost to atmosphere). In order toovercome the wastefulness of continuous delivery, related-art devicesmay operate in conserve mode using a conserver system.

A conserver system may be a device which senses a patient's inspiration,and delivers a bolus of therapeutic gas only during inspiration. Bydelivering therapeutic gas only during inspiration, the amount oftherapeutic gas lost to atmosphere may be reduced. Conserver systems ofthe related art may sense a patient's inspiration at one nare anddeliver the bolus of therapeutic gas to the other nare, such as througha bifurcated nasal cannula. Alternatively, conserver devices of therelated art may sense a patient's inspiration at the nares generally,and delivery a bolus of therapeutic gas to the nares generally, such asthrough a non-bifurcated (single lumen) nasal cannula.

Sensing at one naris and delivering to a second naris may not workproperly in all situations. If the patient has a blocked nare (e.g.,because of congestion or some physical abnormality), either the sensingmay not operate properly or the delivery of therapeutic gas may be tothe blocked nare. Sensing and/or delivery may also fail to operateproperly if the nasal cannula becomes dislodged, such as during sleep.

When sensing inspiration by monitoring both nares simultaneously,congestion and/or abnormalities in the nares may cause the system to notsense properly. Moreover, when delivering therapeutic gas to the naresgenerally, such as through a single lumen cannula, congestion and/orphysical abnormalities of the nares may affect the volume inhaled ineach naris, wasting therapeutic gas in some cases and not providingsufficient therapeutic gas in other cases.

SUMMARY

According to a first aspect there is provided a method comprising:receiving a prescription titration volume, the prescription titrationvolume being generated by titrating a patient with therapeutic gasduring a period of time when a flow state of breathing orifices is in afirst state; receiving an indication that a flow state of the breathingorifices is in a second state different than the first state; andoutputting a control signal arranged to cause the prescription titrationvolume of therapeutic gas to be delivered to the patient only to thebreathing orifices open to flow.

Receiving a prescription titration volume may comprise: receivingindividually sensed airflow of a plurality of the breathing orifices ofthe patient; determining whether the breathing orifices are open toflow, the determining based on the individually sensed airflow of aplurality of the breathing orifices; outputting a control signalarranged to cause a bolus of therapeutic gas to be provided to eachbreathing orifice that is open to flow, the providing during each of aplurality of inhalations of the patient, each bolus has a volume;receiving a measured oxygen saturation of the patient; determining anadjusted set point volume of the bolus; repeating the receivingindividually sensed airflow, outputting, receiving a measured oxygensaturation and determining steps until the patient's oxygen saturationresides within a predetermined range; and calculating the prescriptiontitration volume as a sum of the volumes of each bolus provided duringan inhalation when patient's oxygen saturation resides within thepredetermined range.

Receiving a prescription titration volume may further comprise:receiving individually sensed airflow of each of a first nare and asecond nare of the patient; determining whether the first and secondnares are open to flow, the determining based on the receivedindividually sensed airflow; outputting a control signal arranged tocause a bolus of therapeutic gas to be provided to each nare that isopen to flow, the providing during each of a plurality of inhalations ofthe patient, each bolus has a volume; receiving a measured oxygensaturation of the patient; determining an adjusted set point volume ofthe bolus; repeating the receiving individually sensed airflow,outputting, receiving a measured oxygen saturation and determining stepsuntil the patient's oxygen saturation resides within a predeterminedrange; and calculating the prescription titration volume as a sum of thevolumes of each bolus provided during an inhalation when patient'soxygen saturation resides within the predetermined range.

The prescription titration volume may be generated by titrating thepatient with therapeutic gas during the first state wherein both naresof the patient are open to flow, the titrating results in theprescription titration volume; and the output control signal may bearranged to cause therapeutic gas to be delivered to the patient bydelivering therapeutic gas in the second state wherein only one nare isopen to flow, the delivering by providing prescription titration volumeonly to the nare open to flow.

The prescription titration volume may be generated by titrating thepatient with therapeutic gas during the first state wherein only onenare of the patient is open to flow, the titrating results in theprescription titration volume; and the output control signal may bearranged to cause therapeutic gas to be delivered during the secondstate wherein both nares are open to flow, the delivering by providing afirst non-zero portion of the prescription titration volume to a firstnare and providing a second portion of the prescription titration volumeto a second nare.

The output control signal may be arranged to cause gas to be deliveredby, during each inhalation: receiving individually sensed airflow of thebreathing orifice of the patient; determining whether the breathingorifices are open to flow, the determining based on the individuallysensed airflow; and outputting a signal arranged to cause theprescription titration volume to be divided among the breathing orificesopen to flow.

The output control signal may be arranged to cause gas to be deliveredby, during an inhalation: receiving individually sensed airflow of afirst breathing orifice and a second breathing orifice of the patient;determining initially that the first breathing orifice is open to flowand the second breathing orifice is closed to flow, the determiningbased on the individually sensing; outputting a control signal arrangedto cause delivery of the therapeutic gas to the first breathing orificeto begin; and then determining that during the inhalation the secondbreathing orifice opens to flow; and outputting a control signalarranged to cause delivery of the therapeutic gas to begin to the secondbreathing orifice after beginning delivery of therapeutic gas to thefirst breathing orifice; and outputting a control signal arranged tocause delivery of therapeutic gas to cease to both orifices when thetotal volume delivered is the prescription titration volume.

According to a second aspect of the invention there is provided a methodcomprising: titrating a patient with therapeutic gas during a period oftime when a flow state of breathing orifices is in a first state, thetitrating results in a prescription titration volume; and thendelivering the prescription titration volume of therapeutic gas to thepatient when the flow state of the breathing orifices is in a secondstate different than the first state, the delivering only to thebreathing orifices open to flow.

Titrating may further comprise: individually sensing airflow of aplurality of the breathing orifices of the patient; determining whetherthe breathing orifices are open to flow, the determining based on theindividually sensing; providing a bolus of therapeutic gas to eachbreathing orifice that is open to flow, the providing during each of aplurality of inhalations of the patient, each bolus has a volume;measuring oxygen saturation of the patient; adjusting a set point volumeof the bolus; repeating the sensing, providing, measuring and adjustingsteps until the patient's oxygen saturation resides within apredetermined range; and calculating the prescription titration volumeas a sum of the volumes of each bolus provided during an inhalation whenpatient's oxygen saturation resides within the predetermined range.

Titrating may further comprise: individually sensing airflow of each ofa first nare and a second nare of the patient; determining whether thefirst and second nares are open to flow, the determining based on theindividually sensing; providing a bolus of therapeutic gas to each narethat is open to flow, the providing during each of a plurality ofinhalations of the patient, each bolus has a volume; measuring oxygensaturation of the patient; adjusting a set point volume of the bolus;repeating the sensing, providing, measuring and adjusting steps untilthe patient's oxygen saturation resides within a predetermined range;and calculating the prescription titration volume as a sum of thevolumes of each bolus provided during an inhalation when patient'soxygen saturation resides within the predetermined range.

Titrating may further comprise titrating the patient with therapeuticgas during the first state wherein both nares of the patient are open toflow, the titrating results in the prescription titration volume; andwherein delivering therapeutic gas to the patient may further comprisedelivering therapeutic gas in the second state wherein only one nare isopen to flow, the delivering by providing prescription titration volumeonly to the nare open to flow.

Titrating the patient with therapeutic gas may further comprisetitrating during the first state wherein only one nare of the patient isopen to flow, the titrating results in the prescription titrationvolume; and delivering therapeutic gas to the patient may furthercomprise delivering therapeutic gas during the second state wherein bothnares are open to flow, the delivering by providing a first non-zeroportion of the prescription titration volume to a first nare andproviding a second portion of the prescription titration volume to asecond nare.

Delivering therapeutic gas may further comprise, during each inhalation:individually sensing airflow of the breathing orifice of the patient;determining whether the breathing orifices are open to flow, thedetermining based on the individually sensing; and delivering thetherapeutic gas by dividing the prescription titration volume among thebreathing orifices open to flow.

Delivering therapeutic gas may further comprise, during an inhalation:individually sensing airflow of a first breathing orifice and a secondbreathing orifice of the patient; determining initially that the firstbreathing orifice is open to flow and the second breathing orifice isclosed to flow, the determining based on the individually sensing;beginning delivery of the therapeutic gas to the first breathingorifice; and then determining that during the inhalation the secondbreathing orifice opens to flow; and beginning delivery of thetherapeutic gas to the second breathing orifice after beginning deliveryof therapeutic gas to the first breathing orifice; and ceasing deliveryof therapeutic gas to both orifices when the total volume delivered isthe prescription titration volume.

According to a further aspect there is provided a conserver systemcomprising: a therapeutic gas port configured to couple to a source oftherapeutic gas; a first port configured to fluidly couple to a firstbreathing orifice of a patient; a second port configured to fluidlycouple to a second breathing orifice of the patient; wherein, during afirst inhalation of a patient, the conserver system fluidly couples thegas port to the first port when airflow through the first breathingorifice is sensed by the conserver system, and the conserver systemrefrains from fluidly coupling the gas port to the second port whenairflow through the second breathing orifice is not sensed by theconserver system; wherein, during the first inhalation, the conserversystem decouples the gas port from the first port when a volume oftherapeutic gas delivered to the first port equals a prescriptiontitration volume; wherein, during a second inhalation, the conserversystem fluidly couples the gas port to the first port when airflowthrough the first breathing orifice is sensed, and the conserver systemfluidly couples the gas port to the second port when airflow through thesecond breathing orifice is sensed; and wherein, during the secondinhalation, the conserver system decouples the gas port from the firstand second ports during the second inhalation when a volume oftherapeutic gas delivered to the first and second breathing orificesequals the prescription titration volume.

The order of the inhalations may be at least one selected from the groupconsisting of: the first inhalation precedes the second inhalation; thesecond inhalation precedes the first inhalation; the first inhalationimmediately precedes the second inhalation; the second inhalationimmediately precedes the first inhalation.

The conserver system may further comprise a pressure sensor fluidlycoupled to the first port, the pressure sensor configured to senseairflow of the first breathing orifice based on changes in sensedpressure.

The conserver system may comprise a sensor fluidly associated with thesecond port, the second sensor being at least one selected from thegroup consisting of: a pressure sensor; and a flow sensor.

The conserver system may further comprise a flow sensor fluidly coupledwithin the flow path of the first port, the flow sensor configured tosense airflow of the first breathing orifice drawn through the firstport.

The conserver system may further comprise a sensor fluidly associatedwith the second port, the second sensor being at least one selected fromthe group consisting of: a pressure sensor; and a flow sensor.

During the second inhalation the conserver system may couple the gasport to the first port prior to coupling the gas port to the secondport.

Aspects of the various embodiments may be combined. For example, theconserver system may be arranged to carry out a method according to thefirst or second aspect of the invention. It will be appreciated thataspects of the various embodiments can be implemented in any convenientform. For example, various aspects may be implemented by appropriatecomputer programs which may be carried on appropriate carrier mediawhich may be tangible carrier media (e.g. disks) or intangible carriermedia (e.g. communications signals). Various aspects may also beimplemented using suitable apparatus which may take the form ofprogrammable computers running computer programs arranged to implementthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the various embodiments, reference willnow be made to the accompanying drawings in which:

FIG. 1 shows a delivery system in accordance with at least someembodiments of the invention;

FIG. 2A shows, in shorthand notation, the system of FIG. 1;

FIG. 2B shows an alternative embodiment of the system of FIG. 1;

FIG. 2C shows yet another alternative embodiment of the system of FIG.1;

FIG. 3 shows a delivery system in accordance with alternativeembodiments;

FIG. 4A shows, in shorthand notation, the system of FIG. 3;

FIG. 4B shows an alternative embodiment of the system of FIG. 3;

FIG. 4C shows yet another alternative embodiment of the system of FIG.3;

FIG. 5 shows an alternative embodiment of the system of FIG. 3 usingfewer three-port valves;

FIG. 6 illustrates, in shorthand notation, a delivery system usingmultiple types of sensing devices;

FIG. 7 shows a method in accordance with at least some embodiments;

FIG. 8 shows a method in accordance with at least some embodiments;

FIG. 9 shows a method in accordance with at least some embodiments; and

FIG. 10 shows a method in accordance with at least some embodiments.

DEFINITIONS AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. This document does not intendto distinguish between components that differ in name but not function.

“Prescription titration volume” shall mean a volume of therapeutic gasprovided at each inhalation, and shall not mean that the prescriptiontitration volume is divided among a plurality of breaths.

“Nares” shall mean the nostrils of a patient.

“Nare” shall mean a single nostril of a patient, and is the singular of“nares.”

“Flow state of breathing orifices” shall refer to a flow state of a setof breathing orifices at a particular point in time. For example,considering only the nares of a patient as the set of breathingorifices, each naris can be open to flow (designated as “O” below) orblocked to flow (designated as “B” below), and thus the flow state ofthe breathing orifices in the example set being the left nare and theright nare (in that order) may take any one of the following states: {O,O}, {O, B}, {B, O}, and {B, B}. Similarly, in a set being the left nare,the right nare, and mouth (in that order) the flow state may take anyone of the following flow states: {O, O, O}, {O, B, O}, {B, O, O}, {B,B, O}, {O, O B}, {O, B, B}, and {B, O, B}.

The bolus delivery location control described in this specification isbased on sensing whether breathing orifices are open to flow, andensuring that substantially only the prescription titration volume isprovided in spite of changes in the flow state of breathing orifices ofa patient. Related-art devices may implement a pulse oximetry device tomeasure oxygen saturation in the blood stream, and actively change theamount of therapeutic gas provided to keep oxygen saturation in theblood stream in a predetermined range. However, for purposes of thisspecification and claims, a change in the amount of therapeutic gasprovided responsive directly to oxygen saturation in the blood stream asmeasured by a pulse oximetry device shall be considered a change in theprescription titration volume, and not delivery location control toensure that a previously existing prescription titration volume isprovided in spite of changes in the flow state of the breathingorifices.

“Delivering the prescription titration volume of therapeutic gas to thepatient” shall mean delivering substantially only the prescriptiontitration volume. For purposes of this specification and claims,delivering a volume greater than the prescription titration volume shallnot be considered to include or encompass delivering the prescriptiontitration volume. Stated otherwise, “delivering the prescriptiontitration volume of therapeutic gas to the patient” shall not beconstrued to mean delivering at least the prescription titration volume.

“Substantially”, in relation to a recited volume, shall mean within+/−10% of the recited volume.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect electrical or mechanical connection. Thus, if a first devicecouples to a second device, that connection may be through a directconnection, or through an indirect connection via other devices andconnections.

Various devices or other components in this disclosure may be describedor claimed as “configured to” perform a task or tasks. In such contexts,“configured to” is used to connote structure by indicating that thedevice/component(s) include structure (e.g., circuitry, physicalattributes) that perform those task or tasks during operation. As such,the device/component can be said to be configured to perform the taskeven when the specified device/component is not currently operational(e.g., is not on). The devices/components used with the “configured to”language include hardware—for example, circuits, memory storing programinstructions executable to implements the operation, etc. Reciting thata device/component is “configured to” perform one or more tasks isexpressly intended not to invoke 35 U.S.C. § 112(f) for thatunit/circuit/component.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments. Althoughone or more of these embodiments may be preferred, the embodimentsdisclosed should not be interpreted, or otherwise used, as limiting thescope of the disclosure, including the claims. In addition, one skilledin the art will understand that the following description has broadapplication, and the discussion of any embodiment is meant only to be anexample of the embodiment, and not intended to intimate that the scopeof the disclosure, including the claims, is limited to that embodiment.

The various embodiments are directed to delivery of therapeutic gas byway of bolus control. More particularly, the various embodiments controlon a breath-to-breath basis the location of bolus delivery and bolusvolume based on the flow state of breathing orifices of the patient. Thevarious methods and systems described in this specification weredeveloped in the context of addressing shortcomings of related-artdevices in providing therapeutic gas to a patient. The specificationstarts with a brief description of operation of therapeutic gas deliverysystems of the related art, and then discusses a study that highlightsshortcomings of operation of the related-art systems.

The inventors of the present specification are also co-inventors of U.S.Pat. No. 7,007,692 titled “Method and system of sensing airflow anddelivering therapeutic gas to a patient” (hereafter the '692 Patent),which patent is incorporated by reference herein as if reproduced infull below. The '692 Patent contemplates individually sensing airflow ofthe breathing orifices (e.g., by a pressure sensor, or a flow sensor)and preferentially delivering therapeutic gas to the breathing orificeor orifices that have airflow. In some cases, the delivery is Boolean inthe sense that if airflow is detected, then therapeutic gas isdelivered. In other cases, the '692 Patent discusses deliveringtherapeutic gas in proportion to airflow into the respective breathingorifice (see, e.g., claims 5 and 6 of the '692 Patent). In this way, the'692 Patent may teach reducing waste of therapeutic gas by notattempting to deliver to a breathing orifice that cannot accept thetherapeutic gas.

However, the '692 Patent does not expressly address the effects on thepatient that may result from reducing delivery, or not delivering atall, to breathing orifices that are partially or fully closed to flow.That is, the '692 Patent does not expressly or impliedly contemplate theeffects on the fraction of inspired oxygen (FIO₂) percentage (hereafterjust “inspired oxygen percentage”) within the lungs in situations whereone or more breathing orifices are blocked to flow. The specificationnow turns to summarized results of a study performed regarding theeffects of inspired oxygen percentage as a function of flow state ofbreathing orifices of the patient.

In particular, by way of a confidential study commissioned by theinventors with a Texas university, a series of relationships betweeninspired oxygen percentage within the lungs and the flow state ofbreathings orifices was determined. In particular, the study relatedcontinuous flow oxygen delivered to the nares of an anatomically correctmanikin (including anatomically correct nasal passages) to inspiredoxygen percentage in the lungs for different flow states of the nares(i.e., both nares open, left nare blocked, right nare blocked). Theoxygen was delivered to the manikin by way of a series of dual lumencannulas, each cannula from a different manufacturer. The followingtable summarizes the results.

TABLE 1 Inspired Inspired Inspired Oxygen Oxygen Both Oxygen Left OxygenRight Flow Rate Nares Open Nare Blocked Nare Blocked (LPM) (FIO₂ %)(FIO₂ %) (FIO₂ %) 0.5 24.7 24.3 24.9 1.0 27.7 27.2 27.2 1.5 30.4 29.529.5 2.0 33.8 30.5 31.6 2.5 36.1 31.9 33.6 3.0 38.0 34.3 35.4 3.5 40.434.6 35.3 4.0 40.7 35.4 36.7 4.5 44.2 35.8 39.3 5.0 45.1 35.8 39.8 5.547.3 36.4 40.5 6.0 48.3 38.1 42.1The “Oxygen Flow Rate” is the continuous flow rate of therapeutic gas(in this case oxygen) to the nares of the manikin, with the flow splitevenly between the two lumens of the cannula. The “Inspired Oxygen BothNares Open” is the inspired oxygen percentage in the state with bothnares open to flow. The “Inspired Oxygen Left Nare Blocked” is theinspired oxygen percentage in the state with the right nare open toflow, and the left nare closed to flow. And the “Inspired Oxygen RightNare Blocked” is the inspired oxygen percentage in the state with theleft nare open to flow, and the right nare closed to flow.

The specification next presents a series of scenarios referencing Table1 to highlight shortcomings of the related art identified in the study.

Continuous Flow Scenarios

Scenario 1—Patient Titrated on 2 LPM Continuous Flow, Both Nares Open

In Scenario 1, consider that a patient is titrated using a continuousflow system during a period of time when both patient's nares are opento flow. By titration it is meant that the patient is provided oxygen ata series of differing flow rates until the patient maintains an oxygensaturation in the blood stream at or above a predetermined level (e.g.,above 95%, perhaps during light exercise like walking). The flow ratethat results in the predetermined oxygen saturation may then be selectedby the doctor as the prescription flow rate. Further consider that inScenario 1 the patient's prescription flow rate is set at 2 liter perminute (LPM). From Table 1 it is seen that a flow rate of 2 LPM withboth nares open to flow results in an inspired oxygen percentage of33.8%.

Humans experience what is known as “nasal cycle.” That is, humansperiodically experience unilateral changes in nasal resistance with afrequency of between 25 minutes and 4 hours, with an average of 2.5hours between cycles. Thus, though both nares of a patient may be opento flow during a period of time when titration of the patient is takingplace, the effect of nasal cycle may be to restrict, or close offcompletely, airflow through any particular nare at some point in timethereafter.

Considering Scenario 1 (titration with both nares open, 2 LPMprescription flow rate), if the patient later experiences a blockage ofthe left nare, Table 1 shows that in the test configuration the inspiredoxygen percentage drops to 30.5% (a 3.3% drop in inspired oxygenpercentage). The 30.5% inspired oxygen percentage is about the same as a1.5 LPM flow for the unblocked state (from Table 1, 30.4%), and thus itfollows that the blockage of the left nare in Scenario 1 results in thepatient receiving at least 0.5 LPM too little oxygen flow, which oxygenflow is lost to atmosphere.

Another way to quantify the drop in inspired oxygen percentage is todetermine how much the continuous flow of oxygen would need to increaseto achieve approximately the same inspired oxygen percentage. Lookingagain at Table 1 it is seen than an oxygen flow rate of just under 3 LPMwould be needed to maintain the higher inspired oxygen percentage in theleft nare blocked state (at 3 LPM, Table 1 shows 34.3% for the left nareblocked condition). Stated otherwise, to get the same inspired oxygenpercentage in the left nare blocked state would require a continuousflow of just under 3 LPM (an increase of about 1 LPM over the(non-blocked) titration prescription of 2 LPM).

Scenario 2—Patient Titrated on 3 LPM Continuous Flow, Both Nares Open

In Scenario 2, consider that a patient is titrated using a continuousflow system during a period of time when the patient's nares are bothopen to flow. Further consider that in Scenario 2 the patient'sprescription flow rate is set at 3 LPM. From Table 1 it is seen that aflow rate of 3 LPM with both nares open to flow results in an inspiredoxygen percentage of 38%.

If the patient later experiences a blockage of the left nare, Table 1shows that the inspired oxygen percentage drops to 34.3% (a 3.7% drop ininspired oxygen percentage). The 34.3% inspired oxygen percentage isabout the same as a 2.1 LPM flow for the unblocked state (from Table 1,straight interpolation between 33.8% (for 2 LPM) and 36.1% (for 2.5LPM)), and thus it follows that the blockage of the left nare inScenario 2 results in the patient receiving 0.9 LPM too little oxygenflow, which oxygen flow is lost to atmosphere.

Another way to quantify the drop in inspired oxygen percentage is todetermine how much the continuous flow of oxygen would need to increaseto achieve approximately the same inspired oxygen percentage. Lookingagain at Table 1 it is seen than an oxygen flow rate of just under 6 LPMwould be needed to maintain the higher inspired oxygen percentage in theleft nare blocked state (at 6 LPM, Table 1 shows 38.1% for the left nareblocked condition). Stated otherwise, to get the same inspired oxygenpercentage in the left nare blocked state would require a continuousflow of about 6 LPM (an increase of about 3 LPM over the (non-blocked)titration prescription of 3 LPM).

Scenario 3—Patient Titrated on 3 LPM Continuous Flow, Left Nare Blocked

In Scenario 3, consider that a patient is titrated using a continuousflow system during a period of time when the patient's left nare isblocked to flow but the right nare is open to flow. Further considerthat in Scenario 3 the patient's prescription flow rate is set at 3 LPM.From Table 1 it is seen that a flow rate of 3 LPM with the left nareblocked results in an inspired oxygen percentage of 34.3%.

If the patient later experiences a flow state where both nares are opento flow, Table 1 shows that the inspired oxygen percentage increases to38% (a 3.7% increase in inspired oxygen percentage). The 34.3% inspiredoxygen percentage is about the same as a 2.1 LPM flow for the unblockedstate (from Table 1, straight interpolation between 33.8% (for 2 LPM)and 36.1% (for 2.5 LPM)), and thus it follows that the opening of theleft nare in Scenario 3 results in the patient receiving 0.9 LPM toomuch oxygen flow.

Scenario 4—Patient Titrated on 6 LPM Continuous Flow, Left Nare Blocked

In Scenario 4, consider that a patient is titrated using a continuousflow system during a period of time when the patient's left nare isblocked to flow but the right nare is open to flow. Further considerthat in Scenario 4 the patient's prescription flow rate is set at 6 LPM.From Table 1 it is seen that a flow rate of 6 LPM with the left nareblocked results in an inspired oxygen percentage of 38.1%.

If the patient later experiences a flow state where both nares are opento flow, Table 1 shows that the inspired oxygen percentage increases to48.3% (a 10.2% increase in inspired oxygen percentage). The 38.1%inspired oxygen percentage is about the same as a 3 LPM flow for theunblocked state, and thus it follows that the opening of the left narein Scenario 4 results in the patient receiving 3 LPM too much oxygenflow.

Bolus Flow Scenarios

The specification now turns conserver or bolus flow scenarios. Inparticular, in continuous flow situations the patient is provided acontinuous flow of oxygen at the prescription flow rate; however, oxygendelivered during exhalation (and the rest period between inhalation andexhalation) provides no therapeutic value. Moreover, even oxygen that isinhaled during later portions of an inspiration may not travelsufficiently far into the lungs to provide therapeutic value. Thus, insome situations (e.g., mobile oxygen delivery from a bottle of limitedvolume) a patient is supplied therapeutic gas in a conserver mode, wherea bolus of therapeutic gas is provided only at the beginning of eachinhalation. Published relationships indicate that for every 1 LPM ofcontinuous flow prescription the equivalent bolus delivery is 16.5milliliters (ml) at the beginning of the inhalation. The followingscenarios highlight that, even in the case of bolus delivery, nasalcycle may result in a patient receiving too little therapeutic gas (andthe balance being wasted), or the patient receiving too much therapeuticgas. Note that it is possible to titrate a patient with a conserverdelivery system; however, to better tie the following scenarios to theprevious scenarios it will be assumed that the patient is titrated witha continuous flow system, and the relationship given above (i.e., 16.5ml bolus for every 1 LPM continuous flow prescription) is used tocorrelate to the bolus delivery system.

Scenario 5—Patient Titrated on 2 LPM Continuous Flow, Both Nares Open

In Scenario 5, consider that a patient is titrated using a continuousflow system during a period of time when the patient's nares are bothopen to flow. Further consider that in Scenario 5 the patient'sprescription flow rate is set at 2 liter per minute (LPM). Thus,Scenario 5 is related to Scenario 1. However, using the relationshipgiven above, for a 2 LPM prescription flow rate, in conserver or bolusflow mode 33 ml is provided at each inhalation, being 16.5 ml providedto each nare by way of a bifurcated nasal cannula. If the patient laterexperiences a blockage of the left nare, the 16.5 ml provided to theleft nare is not inhaled by the patient. The patient not only gets toolittle therapeutic gas flow, the 16.5 ml provided to the blocked nare iswasted to atmosphere.

Considered from the standpoint of continuous flow, the loss of 16.5 mlof flow to the patient equates to a drop in continuous flow equivalentof about 1 LPM. This drop in continuous flow equivalent is about thesame as the drop in Scenario 1.

Scenario 6—Patient Titrated on 3 LPM Continuous Flow, Left Nare Blocked

In Scenario 6, consider that a patient is titrated using a continuousflow system during a period of time when the patient's left nare isblocked to flow but the right nare is open to flow. Further considerthat in Scenario 6 the patient's prescription flow rate is set at 3 LPM.Thus, Scenario 6 is related to Scenario 3. However, using therelationship given above, for a 3 LPM prescription flow rate, inconserver or bolus flow mode 49.5 ml is provided at each inhalation,being 24.75 ml provided to each nare by way of a bifurcated nasalcannula. However, because the left nare is blocked, only about 24.75 mlof therapeutic gas makes its way to the patient's lungs during eachinhalation. If the patient later experiences a flow state where bothnares open to flow, the patient receives the full 49.5 ml during eachinhalation. The patient thus receives too much therapeutic gas flow.

Considered from the standpoint of continuous flow, the additional 24.75ml of flow to the patient equates to an increase in continuous flowequivalent of about 1.5 LPM. This increase in continuous flow equivalentis about the same as the increase in Scenario 3.

Summarizing the Scenarios

From the continuous flow study results, and the related bolus flowscenarios, it is seen that merely ceasing delivery to a breathingorifice that has become blocked since titration, while savingtherapeutic gas, may result in providing too little therapeutic gas tothe patient. Likewise, delivering therapeutic gas to a breathing orificethat has opened since titration may result in provide too muchtherapeutic gas to the patient. The various embodiments of the currentdisclosure, discussed in detail below, address (at least in part) theshortcomings of identified.

Before proceeding, it is noted that the study results of Table 1represent a situation of a particular size and arrangement of nasalpassages (in the manikin of the study). Humans come in many shapes andsizes, and it is acknowledged that the specific numbers of Table 1 arenot necessarily accurate for all humans; however, the study results canand do represent trends in changes in inspired oxygen percentage formost if not all humans, and thus the inventors respectfully submit thatsuch results are applicable to the human population as a whole.

Example Systems

With the study results and the shortcomings of the related-arthighlighted based on the study results, the specification now turns to adescription of various embodiments which address, at least in part, theshortcomings noted, starting with a description of systems which may beused to provide therapeutic gas.

FIG. 1 shows a delivery system 100 in accordance with at least someembodiments. The delivery system 100 may be coupled to a therapeutic gassource 10 by way of a gas port 11. The therapeutic gas source 10 may beany suitable source of therapeutic gas, such as a portable cylinder, anoxygen concentration system or a permanent supply system as in ahospital. The delivery system also couples to a patient (not shown) byany of a variety of devices and systems by way of a variety of ports,such as nare ports 23, 25 and an oral port 27. For example, the deliverysystem 100 may couple to a patient's nares by way of a nasal cannula. Inaccordance with at least some embodiments, the delivery system 100monitors patient breathing and delivers therapeutic gas to a left nare(LN), right nare (RN) and/or to the mouth (M) of the patient when thenares/mouth is/are open to flow.

In accordance with at least some embodiments, the delivery system 100comprises both electrical components and mechanical components. In orderto differentiate between electrical connections and mechanicalconnections, FIG. 1 (and the remaining figures) illustrate electricalconnections between components with dashed lines, and fluid connections,e.g. tubing connections between devices, with solid lines. The deliverysystem 100 of FIG. 1 comprises a processor 12. The processor 12 may be amicrocontroller, and therefore the microcontroller may be integral withread-only memory (ROM) 14, random access memory (RAM) 16, adigital-to-analog converter (D/A) 18, and an analog-to-digital converter(ND) 20. The processor 12 may further comprise communication logic 17,which enables the system 100 to communicate with external devices. Thecommunication logic 17 may, for example, transfer stored data about apatient's breathing patterns to external agents, or write the data aboutthe patient's breathing patterns to a removable memory card, such as amemory card read/write device 15 and memory card 19 (e.g., a securedigital (SD) nonvolatile memory card). Although a microcontroller may beused, in alternative embodiments the processor 12 may be implemented bya stand-alone central processing unit in combination with individualRAM, ROM, communication D/A and ND devices.

The ROM 14 stores instructions executable by the processor 12. Inparticular, the ROM 14 may comprise a software program that implementsthe various embodiments discussed herein. The RAM 16 may be the workingmemory for the processor 12, where data may be temporarily stored andfrom which instructions may be executed. Processor 12 may couple toother devices within the preferential delivery system by way of NDconverter 20 and D/A converter 18.

The example delivery system 100 also comprises three-port valve 22,three-port valve 24, and three-port valve 26. In accordance with variousembodiments, each of these three-port valves may be a five-volt solenoidoperated valve that selectively couples one of two ports to a commonport (labeled as C in the drawings). Three-port valves 22, 24 and 26 maybe Humprey Mini-Mizers having part No. D3061, such as may be availablefrom the John Henry Foster Co., or equivalents. By selectively applyingvoltage on a digital output signal line coupled to the three-port valve22, the processor 12 may be able to: couple gas from the gas source 10to the common port and therefore to the exemplary left nare; and couplethe pressure sensor 28 to the common port and therefore the exemplaryleft nare. Likewise, the three-port valve 24, under command of theprocessor 12, may: couple gas from the gas source 10 to the common portand therefore the exemplary right nare; and couple the pressure sensor30 to the common port and therefore the exemplary right naris. Furtherstill, three-port valve 26 under command of the processor 12, may:couple gas from the gas source 10 to the common port and therefore thepatient's mouth; and couple the pressure sensor 32 to the common portand therefore the mouth. When the pressure sensors 28, 30 and 32 arecoupled to the respective common ports, the processor 12 may read(through corresponding A/D converter 20 input signal lines) pressuresindicative of airflow by the patient through the respective breathingorifice. In alternative embodiments, the pressure sensors 28, 30, and 32couple to the common ports of the valves 22, 24, and 26, respectively,if the pressure sensors can withstand the pressure of the therapeuticgas during bolus delivery without damage. Regardless of the preciseplacement, the processor 12 may be able to determine when the patient isinhaling, and an indication of how much of the air drawn by the patientflows through each of the monitored breathing orifices.

Consider a situation where the delivery system 100 couples to the naresof the patient by way of a bifurcated nasal cannula. As the patientinhales, outlet ports in the nasal cannula proximate to the openings ofeach nare experience a drop in pressure. The drop in pressure may besensed through the nasal cannula and associated hosing by each of thepressure sensors 28 and 30. Likewise, a sensing and delivery tube may beplaced proximate to the patient's mouth, and thus pressure sensor 32 maydetect an oral inspiration by the patient. In accordance with variousembodiments, the delivery system 100 senses whether a patient hasairflow through a monitored breathing orifice, and delivers therapeuticgas to the location or locations in such a manner to ensure thepatient's full prescription titration volume is delivered in spite ofchanges in the flow state of the breathing orifices of the patient.

Still considering the situation where the patient couples to thedelivery system 100 by way of a bifurcated nasal cannula and a separatesensing and delivery tube for the mouth, if there is no obstruction toinhalation in either of the nares or the mouth, therapeutic gas may beprovided to any one or a combination of the nares and the mouth. Shouldthe nasal cannula become partially dislodged, therapeutic gas may beprovided only to the nare where the outlet port of the nasal cannula isstill in operational relationship to the nare. Should the patient'snares become congested or blocked, therapeutic gas may be provided tothe nare that is open.

In accordance with various embodiments, the delivery system 100 operatesin a conserve mode, delivering a bolus of gas during each inhalation ofthe patient. Consider for purposes of explanation the left nare port 23illustrated in FIG. 1, as well as its associated three-port valve 22 andpressure sensor 28. Prior to an inhalation, the three-port valve 22 maycouple the pressure sensor to the common port of three-port valve 22 andtherefore the left nare. As the patient starts an inhalation, as sensedby the pressure sensor 28 and read by processor 12, the three-port valve22 changes valve position (as commanded by processor 12) and couples thetherapeutic gas source 10 to the common port (and effectively blocks thepressure sensor 28 from the common port). The therapeutic gas flows tothe exemplary left nare for a period of time to provide the prescriptiontitration volume (or portion thereof). When the desired bolus volume hasbeen delivered (e.g., as function of flow rate of the therapeutic gasand time) the processor 12 commands the three-port valve 22 to itsoriginal state, again fluidly coupling the pressure sensor 28 to theleft naris. During exhalation, again sensed by pressure sensor 28, thethree-port valve 22 remains in the valve position coupling the pressuresensor to the common port, and therefore no therapeutic gas isdelivered. The exemplary process is equally applicable to three-portvalve 24 and pressure sensor 30 in operational relationship to the rightnare, as well as three-port valve 26 and pressure sensor 32 inoperational relationship to the patient's mouth. Thus, the deliverysystem 100 detects whether the nares and/or mouth are open totherapeutic gas flow with each inspiration. In the event an inspirationon any particular delivery path is not detected, indicating a blockageor other gas delivery problem, the delivery system 100 refrains fromproviding therapeutic gas to that breathing orifice, and increases thevolume to the remaining breathing orifices to ensure the patient'sprescription titration volume is provided.

FIG. 2A illustrates the delivery system 100 of FIG. 1 in a shorthandnotation, showing only pressure sensors 28, 30 and 32 coupled to therespective breathing orifices. FIG. 2B illustrates alternativeembodiments monitoring and delivering therapeutic gas only to the naresof a patient. In the embodiments of FIG. 2B, if both the left nare andright nare are open to flow the delivery system 100 may delivertherapeutic gas to either nare, to both nares, or in an alternatingfashion, but in any event the volume delivered to the open nare(s) iscontrolled to ensure the patient receives the prescription titrationvolume. In the event that either the left or right nare become cloggedor blocked, or if the sensing and delivery tubing (such as a nasalcannula) become dislodged, the delivery system provides the entireprescription titration volume to the nare where airflow is sensed. FIG.2C illustrates alternative embodiments where two pressure sensors areused, but in this case only one pressure sensor is associated with thenares, and the second pressure sensor is associated with the mouth. Inthe embodiments of FIG. 2C, a patient may utilize a single lumen cannulaassociated with the nares and a second sensing and delivery tubeassociated with the mouth. The delivery system 100 may thus selectivelyprovide therapeutic gas to the nares and/or to the mouth. In the eventthat either of the nares as a group or the mouth become blocked orotherwise unavailable for inspiration, the delivery system 100 providesthe full prescription titration volume to the breathing orifice throughwhich inhalation takes place.

FIG. 3 illustrates a delivery system 102 constructed in accordance withalternative embodiments. Like the system of FIG. 1, the delivery system102 comprises a processor 12, possibly in the form of a microcontroller,comprising ROM 14, RAM 16, a D/A converter 18, and an ND converter 20.The delivery system 102 may also enable external communications throughthe communication logic 17 and data writing to a memory cardreader/writer, but those abilities are not shown in FIG. 3 so as not tofurther complicate the figure. In the system of FIG. 3, rather thanusing pressure sensors, flow sensors 40, 42 and 44 are used. Thus, thedelivery system 102 may sense a portion of the flow associated with eachbreathing orifice. Consider for purposes of explanation the flow sensor40 and three-port valves 46, 48 coupled to the left nare. Three-portvalve 46, under command of the processor 12, may: couple the gas source10 to the common port and therefore the exemplary left nare; and couplethe flow sensor 40 to the common port and therefore the exemplary leftnare. Thus, during a period of time when the delivery system 102provides therapeutic gas to the left nare, the three-port valve 46provides the therapeutic gas to the left nare and blocks the flowsensor. In a second valve position, the three-port valve 46 fluidlycouples the flow sensor to the common port and therefore the exemplaryleft nare. However, flow sensor 40 may not be operational until gas canflow through the sensor. Three-port valve 48, in a first valve position,couples the flow sensor 40 to an atmospheric vent (marked ATM in thedrawing), thus allows air to flow through the flow sensor formeasurement purposes. The three-port valve 48, in a second valveposition, couples to a blocked port 49. Consider for purposes ofexplanation a delivery system 102 operating in a conserve mode. After abolus has been delivered, the three-port valve 46 may change valvepositions, thus fluidly coupling the flow sensor 40 to the common portand the exemplary left nare. If the flow sensor 40 outlet is notblocked, a portion of the therapeutic gas may reverse flow through theflow sensor 40 and out the atmospheric vent. Three-port valve 48 (aswell as corresponding three-port valves 52 and 56) may be used totemporarily block reverse flow and loss of therapeutic gas, i.e. thevalves may remain in a position that blocks flow for about 300milliseconds after therapeutic gas delivery has stopped by a change ofvalve position by upstream three-port valves 46, 50 and 54. After theexpiration of the period of time of possible reverse flow has ended, oneor more of the three-port valves 48, 52 and 56 may change valvepositions, thus allowing the flow sensors to sense airflow. Thedescription with respect to the three-port valves 46, 48 and flow sensor40 for the left nare is equally applicable for the correspondingstructures for the right naris and mouth.

FIG. 4A illustrates the delivery system 102 of FIG. 3 in a shorthandnotation, showing only flow sensors 40, 42 and 44 coupled to theirrespective breathing orifice. FIG. 4B illustrates alternativeembodiments where only a patient's nares are used for sensing anddelivery. In the embodiments of FIG. 4B, if both the left nare and rightnare are open to flow the delivery system 102 delivers therapeutic gasto either nare, to both nares, or in an alternating fashion, but in anyevent the volume delivered to the open nare(s) is controlled to ensurethe patient receives the prescription titration volume. In the eventthat either the left or right nare become clogged or blocked, or if thesensing and delivery tubing (such as a nasal cannula) become dislodged,the delivery system provides the entire prescription titration volume tothe nare where airflow is sensed. FIG. 4C illustrates furtheralternative embodiments where two flow sensors are used, but in thiscase only one flow sensor is associated with the nares, and the secondflow sensor associated with the mouth. In the embodiments of FIG. 4C, apatient may utilize a single lumen cannula associated with the nares,and a second sensing and delivery tube associated with the mouth. Thedelivery system 102 may thus selectively provide therapeutic gas to thenares and/or the mouth. In the event that either of the nares as a groupor the mouth become blocked or otherwise unavailable for inspiration,the delivery system 102 provides the full prescription titration volumeto the breathing orifice through which inhalation takes place.

FIG. 5 illustrates alternative embodiments utilizing flow sensors, butreducing the number of three-port valves used. The electrical componentshave been omitted from FIG. 5 for purposes of clarity. In particular,FIG. 5 illustrates that the three three-port valves 48, 52 and 56 ofFIG. 3 may be replaced by a single three-port valve 58. Blocking reverseflow through the flow sensors in the embodiments of FIG. 5 may beaccomplished by single three-port valve 58. Relatedly, opening thesecond port of each of the flow sensors to the atmosphere vent so thatflow may be detected may likewise be accomplished with a singlethree-port valve 58.

The example systems need not have only one type of sensor. In yet stillfurther cases, a single system may have both pressure sensors and flowsensors. For example, the size of the nares in relation to airflow drawnthrough nares lends itself well to detection using pressure sensors.However, given the size of the mouth (when open) in relation to theamount of airflow drawn into the mouth (particularly when the nares arealso open flow), better sensing may be achieved using a flow sensor.FIG. 6 shows, in the shorthand notation of FIGS. 2A-C and 4A-C, a systemin which pressure sensors are used for sensing at the nares, and apressure sensor is used for sensing at the mouth.

Bolus Volume Control

The specification now turns to bolus control. As described above, thesystems in accordance with various embodiments control the bolus volumessuch that the patient receives the full prescription titration volumeregardless of the changing flow states of the breathing orifices. Onebolus control implementation involves controlling delivery time to eachbreathing orifice. In particular, and considering the system 100 of FIG.1 as an example, the gas source 10 provides therapeutic gas at aparticular pressure. In the case of a therapeutic gas bottle, a pressureregulator may provide a relatively constant therapeutic gas pressure (inspite of the loss of pressure in the bottle with continued use). In thecase of use of the system 100 in a hospital, the gas source may betherapeutic gas available in the room of the patient, again at apredetermined and controlled pressure. To control the volume oftherapeutic gas delivered to each breathing orifice, an amount of timerespective three-port valves 22, 24, and 26 couple the gas source to theports 23, 25, and 27, respectively, may be controlled. Considering thethree-port valve 22 and the left nare port 23 as an example. Dependingon the size of tubing within the systems 100, and the size and length ofthe tubing fluidly coupling the left nare port 23 to the patient, thethree-port valve 22 is opened for period of time to enable the volume oftherapeutic gas to flow to the patient—longer times result in greatervolume, and shorter times result in lesser volumes.

Consider a situation where a patient is titrated during a period of timewhen both the first and second nares are open to flow. The titrationresults in determining a prescription titration volume (e.g., inmilliliters per inhalation for bolus delivery). During periods of timewhen both nares are open to flow, the respective three port valves areopened for a first amount of time to equally split the overallprescription titration volume between the two nares. Now consider thatthe left nare becomes blocked to flow. In the example situation,related-art devices merely refrained from providing therapeutic gas tothe blocked nare, and only flowed therapeutic gas to the open nare forthe same first amount of time used in the case where both nares wereopen to flow. Thus related-art devices do not account for lowering ofinspired oxygen percentage in the case where one nare becomes blocked.In accordance with the example systems and methods, and in the examplesituation where titration takes place with both nares open to flow butlater one nare becomes blocked, the amount of therapeutic gas to theopen nare is increased by increasing the amount of time the three-portvalve enables therapeutic gas flow to the open nare. Again, in this waythe patient receives the full prescription titration volume in spite ofthe change in the flow state of the breathing orifices of the patient.

Now consider the reverse situation—the patient is titrated with one nareblocked, but later the both nares open to flow. During periods of timeonly one nare is open to flow, the three-port valve associated with theopen nare is opened for a first amount of time to provide the fullprescription titration volume to the open nare. Now consider that theformerly blocked nare opens to flow. In the example situation,related-art devices merely provide therapeutic gas to the newly openednare for the first amount of time. Thus related-art devices do notaccount for the increase of inspired oxygen in the case where one nareis initially blocked but then later opens to flow. In accordance withthe example systems and methods, and in the example situation wheretitration takes place with only one nare open to flow but later bothnares are open to flow, the amount of therapeutic gas to the originallyopen nare is decreased by decreasing the amount of time the three-portvalve enables therapeutic gas flow to the formerly open nare, and thenewly opened nare is provided therapeutic gas for an equal amount oftime. Again, in this way the patient receives only the full prescriptiontitration volume in spite of the change in the flow state of thebreathing orifices of the patient.

In other cases, the volume of therapeutic gas provided to a breathingorifice may be controlled in other ways, such as by pulse-widthmodulation of the respective three-port valves. Consider again thesituation where a patient is titrated during a period of time when boththe first and second nares are open to flow, and later one nare becomesblocked to flow. During periods of time when both nares are open toflow, the respective three-port valves may be pulse-width modulated at acorresponding first duty cycle to equally split the overall prescriptiontitration volume between the two nares. When the one nare becomesblocked to flow, no flow is provided to the blocked nare, and the amountof therapeutic gas to the open nare is increased by increasing the dutycycle of the three-port valve enables therapeutic gas flow to the opennare. Again, in this way the patient receives the full prescriptiontitration volume in spite of the change in the flow state of thebreathing orifices of the patient.

Now consider the reverse situation—the patient is titrated with one nareblocked, but later the both nares open to flow. During periods of timewhen only one nare is open to flow, the three-port valve associated withthe open nare is pulse-width modulated at a first duty cycle to providethe full prescription titration volume to the right nare. Now considerthat the formerly blocked nare opens to flow. When the newly opened narebecomes open to flow, and the amount of therapeutic gas to theoriginally open nare is decreased by lowering the duty cycle duty cycleof the three-port valve associated with the originally open nare, andproviding therapeutic gas to the newly open left nare at the loweredduty cycle. Again, in this way the patient receives only the fullprescription titration volume in spite of the change in the flow stateof the breathing orifices of the patient.

In the pulse-width modulation cases, it was assumed that the deliverytime (i.e., the amount of time in which pulse-width modulation isperformed) is held constant; however, in yet still further cases anycombination of delivery time and/or pulse-width modulation duty cyclemay be used to control the volume of therapeutic gas provided to eachbreathing orifice to ensure the overall prescription titration volume isdelivered to the patient in spite of changing flow states of thebreathing orifices of the patient.

FIG. 7 shows a flow diagram of a method in accordance with at least someembodiments, some of which may be performed by software executing on aprocessor associated with the delivery system. In particular, the methodstarts (block 700) and proceeds to titrating a patient with therapeuticgas during a period of time when a flow state of breathing orifices isin a first state, the titrating results in a prescription titrationvolume (block 702). The method then involves delivering the prescriptiontitration volume of therapeutic gas to the patient when the flow stateof the breathing orifices is in a second state different than the firststate, the delivering only to the breathing orifices open to flow (block704). Thereafter the method ends (block 706).

FIG. 8 shows a method in accordance with at least some embodiments, someof which may be performed by software executing on a processorassociated with the delivery system. In particular, the method starts(block 800) and proceeds to: individually sensing airflow of a pluralityof the breathing orifices of the patient (block 802); determiningwhether the breathing orifices are open to flow, the determining basedon the individually sensing (block 804); providing a bolus oftherapeutic gas to each breathing orifice that is open to flow, theproviding during each of a plurality of inhalations of the patient, eachbolus has a volume (block 806); measuring oxygen saturation of thepatient (block 808); adjusting a set point volume of the bolus (block810); repeating the sensing, providing, measuring and adjusting stepsuntil the patient's oxygen saturation resides within a predeterminedrange (block 812); and calculating the prescription titration volume asa sum of the volumes of each bolus provided during an inhalation whenpatient's oxygen saturation resides within the predetermined range(block 814). Thereafter the method ends (block 816).

FIG. 9 shows a method in accordance with at least some embodiments, someof which may be performed by software executing on a processorassociated with the delivery system. In particular, the method starts(block 900) and proceeds to: individually sensing airflow of thebreathing orifice of the patient (block 902); determining whether thebreathing orifices are open to flow, the determining based on theindividually sensing (block 904); and delivering the therapeutic gas bydividing the prescription titration volume among the breathing orificesopen to flow (block 906). Thereafter, the method ends (block 908),likely to be restarted on the next inhalation.

FIG. 10 shows a method in accordance with at least some embodiments,some of which may be performed by software executing on a processorassociated with the delivery system. In particular, the method starts(block 1000) and proceeds to a determination as to whether an inhalationof the patient has begun (block 1102). If no inhalation has begun, theexample method loops until inhalation is detected (again block 1102).Once an inhalation has been detected, the example method takes twoparallel paths, one path addressing the left nare, and one pathaddressing the right nare. The description starts along the pathassociated with the left nare. In particular, the example methoddetermines whether there is airflow associated with the left nare (block1106). If no airflow is sensed, the example method loops waiting forairflow (again block 1106). The loop waiting for airflow may be brokenby the lockout delay (1108), discussed more below. Assuming airflow issensed for the left nare (again block 1106), the example method beginstherapeutic gas delivery to the left nare (block 1110). As soon asdelivery is begun, the method also begins to accumulate an indication ofvolume supplied to the left nare (block 1112). For example, in systemswhere the volume is controlled based on delivery time, the indication ofvolume supplied to the left nare may be the delivery time, or an actualvolume indication calculated based on delivery time. The example methodthen makes a determination as to whether the prescription titrationvolume has been provided to the patient (block 1114). The determinationat block 1114 is based on all the breathing orifices to whichtherapeutic gas has been supplied (not just the left nare), and thus thedetermination may involve reference to a stand-alone summing method(block 1116) which sums the accumulated volumes across all the breathingorifices as indicated by the dashed lines associated with the method. Ifthe full prescription titration volume has yet to be provided to patient(again block 1114), the method along the path loops until the fullprescription titration volume is supplied (again block 1114).

Returning to the portion where the method proceeds down the parallelpaths, again, once inhalation has been detected the example method alsoproceeds along the path associated with the right nare. In particular,the example method determines whether there is airflow associated withthe right nare (block 1126). If no airflow is sensed, the example methodloops waiting for airflow (again block 1126). The loop waiting forairflow may be broken by the lockout delay (1108), discussed more below.Assuming airflow is sensed for the right nare (again block 1126), theexample method begins therapeutic gas delivery to the right nare (block1130). As soon as delivery is begun, the method also begins toaccumulate an indication of volume supplied to the right nare (block1132). For example, in systems where the volume is controlled based ondelivery time, the indication of volume supplied to the right nare maybe the delivery time, or an actual volume indication calculated based ondelivery time. The example method then makes a determination as towhether the prescription titration volume has been provided to thepatient (block 1134). The determination at block 1134 is based on allthe breathing orifices to which therapeutic gas has been supplied (andnot just the right nare), and thus the determination may involvereference to the stand-alone summing method (block 1116) which sums theaccumulated volumes across all the breathing orifices as indicated bythe dashed lines associated with the method. If the full prescriptiontitration volume has yet to be provided to patient (again block 1134),the method along the path loops until the full prescription titrationvolume is supplied (again block 1134).

Still referring to FIG. 10, the example method as shown enables not onlysimultaneous delivery to the nares, but also staggered delivery-starttimes. Consider for example, that because of a physical abnormality(e.g., a swollen turbinate) associated with one nare that initially theinhalation is only sensed through the non-blocked nare. In the examplesituation, once airflow is sensed for the non-blocked nare, therapeuticgas delivery is begun. However, further consider that with increasebreathing effort the blocked nare opens to flow (e.g., the swollenturbinate moves out of the way and is thereafter held open by airflowthrough the formerly blocked nare). Once the formerly blocked nare opensto flow (and assuming the full prescription titration volume has yet tobe delivered), the example method begins delivery of therapeutic gas tothe formerly blocked nare (at a finite time after beginning delivery tothe other nare).

Regardless of the timing as between when therapeutic gas delivery beginsto each nare, once the full prescription titration flow has beendelivered, the example method stops delivery of therapeutic gas for allbreathing orifices (block 1140). From there, the system implements alockout delay (block 1108), and also breaks any pending loops waitingfor airflow. As for the lockout delay, delivery of therapeutic gasduring the inhalation takes places at the beginning of the inhalation,and the full prescription titration volume may be delivered in a timespan shorter than the time span of the inhalation itself. For example,it may take only 100 milliseconds to deliver a bolus of therapeutic gasthat meets the full prescription titration volume, yet the inhalationmay last a second or more. In order to reduce the chances of doubledelivery of therapeutic gas in the same inhalation, the lockout delay(block 1108) implements a time delay to ensure the current inhalationhas ceased before the method begins inhalation detection anew (at block1102). As for the “break loops” aspect, as noted above the examplemethod proceeds along parallel paths. If one nare is blocked to flow(and thus one path may be in a loop waiting for inhalation of that nareto begin), once the full prescription titration volume has been providedthe software loop is broken, thus enabling the method to begin sensinganew (at block 1102) for the next inhalation.

Finally, once the lockout delay (block 1108 has ended), the examplemethod resets the accumulated volumes (block 1142), and begins anew (atblock 1102) sensing the next inhalation.

The example method of FIG. 10 references only the nares of a patient;however, one of ordinary skill, with the benefit of this disclosure andnow understanding the implementation with respect to the nares, couldadapt the method of FIG. 10 to include a parallel path for oraldelivery. Moreover, one of ordinary skill, with the benefit of thisdisclosure and now understanding the implementation with respect to thenares, could adapt the method of FIG. 10 to treat the nares as a singleunit with respect to one of the parallel paths, and treat the mouthalong the second parallel path.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. A conserver system comprising: a therapeutic gasport configured to couple to a source of therapeutic gas; a first portconfigured to fluidly couple to a first breathing orifice of a patient;a first sensor associated with the first port, and a first valve fluidlycoupled between the therapeutic gas port and the first port; a secondport configured to fluidly couple to a second breathing orifice of thepatient; a second sensor associated with the second port, and a secondvalve fluidly coupled between the therapeutic as port and the secondport; a processor electrically coupled to the first sensor and the firstvalve, and the processor electrically coupled to the second sensor andthe second valve; a memory coupled to the processor, the memory storinga program that, when executed by the processor, causes the processor to:fluidly couple, during a first inhalation, the therapeutic gas port tothe first port by way of the first valve when airflow through the firstbreathing orifice is sensed by the first sensor; refrain, during aninitial portion of the first inhalation, from fluidly coupling thetherapeutic gas port to the second port when airflow through the secondbreathing orifice is not sensed by the second sensor; and then fluidlycouple, during a subsequent portion of the first inhalation of thepatient, the therapeutic gas port to the second port by way of thesecond valve when airflow through the second breathing orifice is latersensed by the second sensor; and decouple the therapeutic gas port fromthe first and second ports when a volume of therapeutic gas delivered tothe first and second breathing orifices equals a prescription titrationvolume.
 2. The conserver system of claim 1, wherein the first sensor isa first pressure sensor fluidly coupled to the first port, the firstpressure sensor configured to sense airflow of the first breathingorifice based on changes in sensed pressure.
 3. The conserver system ofclaim 2, wherein the second sensor comprises at least one selected fromthe group consisting of a pressure sensor and a flow sensor.
 4. Theconserver system of claim 1, wherein the first sensor comprises a firstflow sensor fluidly coupled within a flow path of the first port, thefirst flow sensor configured to sense airflow of the first breathingorifice drawn through the first port.
 5. The conserver system of claim4, wherein the second sensor comprises at least one selected from thegroup consisting of a pressure sensor and a flow sensor.
 6. Theconserver system of claim 1, wherein the program further causes theprocessor to: accumulate, during the first inhalation, a firstindication of volume applied to the first breathing orifice; accumulate,during the first inhalation, a second indication of volume applied tothe second breathing orifice; and sum the first and second indicationsof volume to create a first sum value; wherein when the processordecouples the therapeutic gas port from the first and second ports, theprogram further causes the processor to decouple when the first sumvalue meets a value indicative of the prescription titration volume. 7.The conserver system of claim 1, wherein the program further causes theprocessor to: fluidly couple, during a second inhalation of the patient,the therapeutic gas port to the second port by way of the second valvewhen airflow through the second breathing orifice is sensed by thesecond sensor; refrain, during an initial portion of the secondinhalation of the patient, from fluidly coupling the therapeutic gasport to the first port when airflow through the first sensor is notsensed; and then fluidly couple, during a subsequent portion of thesecond inhalation of the patient, the therapeutic gas port to the firstport by way of the first valve when airflow through the first breathingorifice is later sensed by the first sensor; and decouple thetherapeutic gas port from the first and second ports when a volume oftherapeutic gas delivered to the first and second breathing orificesduring the second inhalation equals the prescription titration volume.8. The conserver system of claim 7, wherein the program further causesthe processor to: accumulate, during the second inhalation, a thirdindication of volume applied to the first breathing orifice; accumulate,during the second inhalation, a fourth indication of volume applied tothe second breathing orifice; and sum the third and fourth indicationsof volume to create a second sum value; wherein when the processordecouples the therapeutic gas port from the first and second portsassociated with the second inhalation, the program further causes theprocessor to decouple when the second sum value meets the valueindicative of the prescription titration volume.
 9. A conserver systemcomprising: a therapeutic gas port disposed on an outside surface of theconserver system; a first port disposed on an outside surface of theconserver system, a first sensor associated with the first port, and afirst valve fluidly coupled between the therapeutic gas port and thefirst port; a second port disposed on an outside surface of theconserver system, a second sensor associated with the second port, and asecond valve fluidly coupled between the therapeutic gas port and thesecond port; a processor electrically coupled to the first sensor, thefirst valve, the second sensor, and the second valve; a memory coupledto the processor, the memory storing a program that, when executed bythe processor, causes the processor to, during a first inhalation:fluidly couple the therapeutic gas port to the first port by way of thefirst valve when airflow through the first port is sensed by the firstsensor; refrain from fluidly coupling the therapeutic gas port to thesecond port when airflow through the second port is not sensed by thesecond sensor during an initial portion of the first inhalation; andthen fluidly couple the therapeutic gas port to the second port by wayof the second valve when airflow through the second breathing orifice islater sensed by the second sensor during a subsequent portion of thefirst inhalation; and decouple the therapeutic gas port from the firstand second ports when a volume of therapeutic gas delivered to the firstand second ports equals a prescription titration volume.
 10. Theconserver system of claim 9: wherein the program further causes theprocessor to, during the first inhalation: accumulate a first indicationof volume applied to the first breathing orifice; accumulate a secondindication of volume applied to the second breathing orifice; and sumthe first and second indications of volume to create a first sum value;wherein when the processor decouples the therapeutic gas port from thefirst and second ports, the program further causes the processor to,during the first inhalation, decouple when the first sum value meets avalue indicative of the prescription titration volume.
 11. The conserversystem of claim 9, wherein the program further causes the processor to,during a second inhalation distinct from the first inhalation: fluidlycouple the therapeutic gas port to the second port by way of the secondvalve when airflow through the second port is sensed by the secondsensor; refrain from fluidly coupling the therapeutic gas port to thefirst port when airflow through the first sensor is not sensed by thefirst sensor during an initial portion of the second inhalation; andthen fluidly couple the therapeutic gas port to the first port by way ofthe first valve when airflow through the first port is later sensed bythe first sensor during a subsequent portion of the second inhalation;and decouple the therapeutic gas port from the first and second portswhen a volume of therapeutic gas delivered to the first and secondbreathing orifices during the second inhalation equals the prescriptiontitration volume.
 12. The conserver system of claim 11: wherein theprogram further causes the processor to, during the second inhalation:accumulate a third indication of volume applied to the first breathingorifice; accumulate a fourth indication of volume applied to the secondbreathing orifice; and sum the third and fourth indications of volume tocreate a second sum value; wherein when the processor decouples thetherapeutic gas port from the first and second ports associated with thesecond inhalation, the program further causes the processor to, duringthe second inhalation, decouple when the second sum value meets thevalue indicative of the prescription titration volume.